Table 20
presents foetal deaths and foetal death ratios by gestational age for as many
years as possible between 1990 and 1998.

Description of
variables: Gestational age for foetal deaths is defined as the interval, in
completed weeks, between the first day of the last menstrual period of the
mother and the day, month and year of delivery.

The
gestational age classification used in this table is as follows under 20 weeks,
20-27 weeks, 28-31 weeks, 32-35 weeks, 36 weeks, 37-39 weeks, 40 weeks and over
and unknown gestational age.Data
tabulated for alternative length of gestational categories are indicated by
footnote.

The three
major categories of foetal death are early foetal death or less than 20
completed weeks of gestation; intermediate foetal death of 20 but less than 28
weeks, and late foetal death of 28 weeks or more.Three dots (...) in lower age groups
indicate that only data on intermediate and/or late foetal deaths are
available.

Ratio
computation: Foetal death ratios by gestational age are the number of foetal
deaths which occurred in each gestational age group during the year per 1
000 total live births which occurred during the same year.The live birth base was adapted because
it is assumed to be more comparable over time from one country or area to
another than the combination of live births and foetal deaths.

All
ratios were computed in the Statistics Division of the United Nations using live
births shown in table 1.

Foetal
deaths of unknown gestational age have not been distributed
proportionately.They are included
only in the total foetal death ratio.

Ratios
presented in this table have been limited to those for countries or areas having
at least a total of 1 000 foetal deaths in a given year.Moreover, ratios specific for individual
sub-categories based on 30 or fewer foetal deaths shown in this table are
identified by the symbol
(g).
These
ratios have been computed by the Statistics Division of the United
Nations.

Reliability of
data: Data from civil registers of late foetal deaths which are reported as
incomplete (less than 90 per cent completeness) or of unknown completeness are
considered unreliable and are set in italics rather than in roman type.Table 15 and the technical notes for
that table provide more detailed information on the completeness of late foetal
death registration. For more information about the quality of vital statistics
in general, and the information available on the basis of the completeness
estimates in particular, see section 4.2 of the Technical Notes.

Limitations:
Statistics on foetal deaths by gestational age are subject to the same
qualifications that have been set forth for vital statistics in general and
foetal death statistics in particular as discussed in section 4 of the Technical
Notes.

The
reliability of data, an indication of which is described above, is an important
factor.Of all vital statistics,
the registration of foetal deaths is probably the most incomplete.

Variation
in the definition of foetal deaths, and in particular late foetal deaths, also
limits international comparability.The criterion of 28 or more completed weeks of gestational age to
distinguish late foetal deaths is not universally used; some countries or areas
use different lengths of gestation or other criteria such as length of the
foetus.In addition, the difficulty
of accurately determining gestational age further reduces
comparability.

Another factor
introducing variation in the definition of late foetal deaths is the practice by
some countries or areas of including in late foetal death statistics infants who
were born alive but died before registration of birth or within the first 24
hours after birth thus overestimating the total number of late foetal
deaths.Statistics of this type are
footnoted.

The
principal factor limiting comparability of data from this table is the variation
in national requirements for registration of foetal deaths.In some countries or areas, registration
is required for all foetal deaths regardless of length of gestation.In other countries or areas,
registration of foetal deaths is only required following a minimum length of
gestation.In the latter case the
minimum varies; both 20 and 28 weeks are common lengths of gestation after which
a foetal death must be registered.

Completeness
of registration further limits the comparability of foetal deaths and
foetal-death ratios.Incomplete
registration may occur even when the minimum gestation for registration is 20 or
28 weeks.Under-reporting is a more
serious problem at the early stages of pregnancy when it is not always possible
to determine whether or not a pregnancy has occurred.

The
estimation and recording of gestational age itself are subject to considerable
uncertainty.In many cases,
gestational age is estimated from the woman's recollection of the date of onset
of the last menstrual period or medical records of this date, while in other
cases gestational age is inferred from the weight or other characteristics of
the foetus or from other information about the probable time of conception.Moreover, gestational age can only be
determined by inference for those conceptions which occur during past-portum
amenorrhoea. Given the considerable variation between countries in the
proportion of conceptions occurring in this period to estimate gestational age,
memory errors and errors arising in the conversion of this date to the
gestational age of the foetus may introduce biases into tabulations by
gestational age.

In
addition, foetal-death ratios are subject to the same data limitations as live
births from which they are computed.These limitations are described in the technical notes for table 1 and
table 15.

Coverage: Foetal
deaths and foetal-death ratios by gestational age are shown for 43 countries or
areas.

Earlier
data: Foetal deaths and foetal-death ratios by gestational age have been shown
previously in issues of the Demographic yearbook.For information on years covered,
readers should consult the Index.